The Emergence of in-Group Friendships in the Absence of Intrinsic in-Group Preference: The Role of Experience and Expectation Formation

A plethora of past research shows that individuals primarily tend to form friendships with other in-group members, such as their same-sex, same-race, or same-age peers. In this paper, I introduce a formal model that attempts to explain how such preferences for friendships among individuals with similar observable characteristics—such as race, sex, or age—can emerge even if they are intrinsically indifferent about these characteristics.

Instead of these readily observable characteristics, the model assumes actors to only be interested in similarity to their friends regarding another set of attributes—characteristics that are hard to observe, such as their sense of humour, leisure time interests, or aspirations. The issue with these characteristics is that they usually only become observable once a relationship has been created, forcing actors to form expectations about these attributes on the basis of their previous experiences when deciding who to become friends with. If the differentiation between the in-group and out-groups is salient, expectations are likely to be formed separately for the groups. At the same time, actors tend to be more experienced with their in-group than the out-group because of different exposure in everyday life. In the model I show that, due to this lack of experience, out-group expectations tend to be both individually more uncertain than in-group expectations and more widely dispersed in the population of actors overall. Higher uncertainty and dispersion of expectations tend to be evaluated negatively if actors prefer similarity on the hard-to-observe attributes, and thus disfavour out-group friendships.

I provide formal results for a static version of the model and investigate dynamic friendship formation—with expectations being updated according to new experiences—using simulations. Finally, I consider how the processes discussed above are amplified or mitigated in the presence of structural constraints to friendship formation.